Celltrion Healthcare has set about to dispel concerns over the poor sales outlook of its Humira biosimilar, Yuflyma (adalimumab), even before it debuted in the U.S. market.

According to industry sources, Celltrion Healthcare's recent failure to put Yuflyma on the Humira biosimilar prescription drug list of Optum RX, one of the top three U.S. pharmacy benefits managers (PBMs), has raised concerns about its ability to compete in the U.S. market.

PBMs are private organizations that negotiate drug availability and pricing with pharmaceutical companies on behalf of insurance companies. Negotiations with PBMs are seen as an important gateway to the U.S. market, as being on a large PBM's formulary means a drug can be prescribed to more insurance subscribers.

Optum RX, which announced three Humira biosimilar products on its list, recently added products from Sandoz and Boehringer Ingelheim, following Amgen's. After the news spread in Korea, stock prices of Celltrion and Celltrion Healthcare fell 14,300 won (8.66 percent) and 5,700 won (8.05 percent), respectively, on Tuesday from the previous day’s closing price.

In response, Celltrion Healthcare posted a shareholder letter on its website on Wednesday to appease shareholders, expressing the company's position that there is no problem entering the U.S. market.

"There is a misunderstanding in the market regarding the PBM pricing of the Humira biosimilar, and we would like to correct it," Celltrion Healthcare said in the shareholder letter. "We are preparing for the launch of Yuflyma in early July to cover 40 percent of the total adalimumab market and are in discussions with PBMs based on the profitability and quality of the product."